ES2375226T3 - USE OF A POLYOLEFINE COMPOSITION THAT INCLUDES RETICULABLE POLYOLEFINE WITH SILANOUS GROUPS, SILANOL CONDENSATION CATALYST AND PIGMENT FOR THE PRODUCTION OF A COAT ON A WIRE OR CABLE. - Google Patents

Abstract

The present invention is directed to particular titanium dioxide containing compositions which allow the retention of a high crosslinking performance of a polyolefin composition comprising a crosslinkable polyolefin with hydrolysable silane groups, a Brönstedt acid silanol condensation catalyst and said titanium dioxide containing composition. The retention of the high crosslinking performance is shown by a difference in torque measured at 120 °C of 40 Nm or higher.

Description

Use of a polyolefin composition comprising crosslinkable polyolefin with silane groups, silanol condensation catalyst and pigment for the production of a layer on a wire or cable

The present invention relates to the use of a polyolefin composition comprising a crosslinkable polyolefin with hydrolysable silane groups, a silanol condensation catalyst and a pigment for the production of a layer of a wire or cable.

It is known to crosslink polyolefins by means of additives as this improves the properties of polyolefin such as mechanical strength and chemical heat resistance. Crosslinking can be carried out by condensation of silanol groups contained in the polyolefin which can be obtained by hydrolyzing silane groups. A silane compound can be introduced as a crosslinkable group, for example, by grafting the silane compound into a polyolefin,

or by copolymerization of olefin monomers and monomers containing silane groups. Such techniques are known, for example, from US 4,413,066, US 4,297,310, US 4,351,876, US 4,397,981, US 4,446,283 and US 4,456,704.

For the crosslinking of such polyolefins a silanol condensation catalyst should be used. Conventional catalysts are, for example, organostannic compounds such as dibutyltin dilaurate (DBTDL). It is further known that the cross-linking process is advantageously carried out in the presence of acid silanol condensation catalysts. Unlike conventional organotin catalysts, acid catalysts allow crosslinking to take place quickly at room temperature. Such acid silanol condensation catalysts are disclosed, for example, in WO 95/17463. The content of that document is included in this document by reference.

It is also known to use various additives in polyolefin compositions. The type and particular amount of additive to be used depends on the particular application for which a polyolefin composition is designed.

An important group among such additives is represented by pigments. One of the most important pigment groups comprises titanium dioxide, TiO2, as the main component. Titanium dioxide is used in these pigments in order to improve the color coverage in the processed article, titanium dioxide makes the material more opaque.

Thus, the use of compositions containing titanium dioxide in polyolefin compositions comprising a polyolefin with hydrolysable silane groups and a conventional silanol condensation catalyst is known in the art.

However, it has now been shown that compositions containing titanium dioxide are deactivating the crosslinking capacity of Brönstedt acids used as silanol condensation catalysts. Therefore, in general terms, compositions containing titanium dioxide are not compatible with the cross-linking technology of polyolefins containing hydrolysable silane groups with a Brönstedt acid as a silanol condensation catalyst.

Therefore, it is an object of the present invention to provide a polyolefin composition comprising a crosslinkable polyolefin with hydrolysable silane groups, a Brönstedt acid silanol condensation catalyst and a titanium dioxide containing composition that does not adversely affect the yield of crosslinking of the Brönstedt acid silanol condensation catalyst.

The crosslinking performance is measured in a batch mixer that measures and represents the torque in the rotors. The polyolefin containing hydrolysable silane groups is mixed with the silanol condensation catalyst and the pigment composition at elevated temperature. After forming a homogeneous fusion, crosslinking begins and, therefore, increases the torque. The degree of crosslinking is given as the difference between the highest value of the torque, measured when the crosslinking is completed or after a maximum reaction time of 2 h, and the lowest value of the torque, measured before it begins crosslinking

It has now been surprisingly found that the above object can be achieved by applying compositions containing particular selected titanium dioxide according to the present invention.

The present invention relates to the use of a polyolefin composition for the production of a layer of a thread

or cable, comprising the polyolefin composition

(i)

 a crosslinkable polyethylene with hydrolysable silane groups (A),

(ii)

 a silanol condensation catalyst (B) which is a Brönstedt acid (B), and

(iii) a composition containing titanium dioxide (C), a) which does not comprise a silicon-containing coating and the concentration of titanium dioxide in said composition containing titanium dioxide is at least 93% by weight, or

b) the titanium dioxide in said composition containing titanium dioxide is coated, coating containing silicon, and the concentration of titanium dioxide in said composition containing titanium dioxide is at least 97% by weight,

characterized in that the difference between the highest torque value, when the crosslinking is completed or after a maximum reaction time of 2 h, and the lower torque value, before the crosslinking begins, both values measured at 120 ° C using a batch laboratory mixer with a capacity to mix 25 to 500 g and that has the option of measuring the melt temperature and the time of the rotors, is 40 Nm or higher.

Preferably, the difference in the torque measured at 120 ° C is 44 Nm or more, more preferably 45 Nm or more, even more preferably 50 Nm or more.

In the case of an uncoated titanium dioxide or in the case that the composition containing titanium dioxide does not comprise a silicon-containing coating, the concentration of titanium dioxide in said composition containing titanium dioxide is preferably at least the 97% by weight and more preferably at least 98% by weight.

It is further preferred that the amount of a titanium dioxide coating of said titanium dioxide containing composition is at most 1% by weight.

Preferably, the titanium dioxide in said composition containing titanium dioxide does not contain any coating.

The compositions allow the retention of a high crosslinking yield of a polyolefin composition comprising a crosslinkable polyolefin with hydrolyzable silane groups, a Brönstedt acid silanol condensation catalyst and a composition containing particular titanium dioxide.

Compositions containing commercially available titanium dioxide typically comprise a titanium dioxide coating. These coatings allow a better dispersion of the pigment composition in the polyolefin composition. Moreover, the coating affects the deformation behavior of a polyolefin composition. Without being bound by any theory, it is believed that the type and amount of coating also affect the compatibility of the respective titanium dioxide-containing composition with the Brönstedt acid silanol condensation catalyst.

Preferably, the compositions containing titanium dioxide contain coated titanium dioxide, but nevertheless achieve the favorable effect of the present invention, specifically allowing the retention of a high crosslinking performance of a polyolefin composition comprising a crosslinkable polyolefin with silane groups. hydrolysable, a Brönstedt acid silanol condensation catalyst and a composition containing particular titanium dioxide. Such compositions are commercially available as Tioxide RFC5, Tioxide TR28, Kemira 300 and Kemira RD3.

Preferably, the compositions containing titanium dioxide do not contain coated titanium dioxide. Particular preferred examples are anatase or uncoated rutile. Such compositions are commercially available as Kemira AN and Tioxide AHR.

It is preferred that the particle size of the titanium dioxide used be greater than 0.10 μm. Even more, it is preferred that the particle size be less than 0.35 μm. It is even more preferred that the particle size be greater than 0.15 μm and less than 0.25 μm.

When the term "particle size" is used in the present invention, it should denote the particle size that is measured with geometric (average) weight distribution with standard deviation using a transmission electron microscopy (TEM) instrument.

Preferably, in the polyolefin composition, the composition containing titanium dioxide is present in an amount of 0.01 to 10% by weight, more preferably 0.1 to 5% by weight, and most preferably 0.5 at 2% by weight.

The Brönstedt acid silanol condensation catalyst (B) is preferably a sulfonic acid, more preferably any organic sulfonic acid. Even more preferably it is an organic sulfonic acid comprising 10 C atoms or more, more preferably 12 C atoms or more, and most preferably 14 C atoms or more, the sulfonic acid further comprising at least one aromatic group which may be , for example, a benzene, naphthalene, phenanthrene or anthracene group. One, two or more sulfonic acid groups may be present in the organic sulfonic acid, and the sulfonic acid group (s) can both be attached to a non-aromatic group, preferably an aromatic group, of the organic sulfonic acid .

More preferred, the aromatic organic sulfonic acid comprises the structural element:

Ar (SO3H) x (II)

Ar being an aryl group that may be substituted or unsubstituted, and x being at least 1.

The organic aromatic sulfonic acid silanol condensation catalyst may comprise the structural unit according to formula (II) once or several times, for example, two or three times. For example, two structural units according to formula (II) can be linked together by a bridge forming group such as an alkylene group.

Preferably, Ar is an aryl group that is substituted with at least one C4 to C30 hydrocarbyl group, more preferably C4 to C30 alkyl group.

The aryl group Ar is preferably a phenyl group, a naphthalene group or an aromatic group comprising three condensed rings such as phenanthrene and anthracene.

Preferably, in the formula (II) x is 1, 2 or 3, and more preferably x is 1 or 2.

In addition, preferably the compound used as a condensation catalyst of organic aromatic sulfonic acid silanol has 10 to 200 C atoms, more preferably 14 to 100 C atoms.

In a preferred embodiment, Ar is a hydrocarbyl-substituted aryl group and the total compound contains 14 to 28 carbon atoms, and even more preferred, the Ar group is a hydrocarbyl-substituted benzene or naphthalene ring, containing the radical or radicals. hydrocarbyl 8 to 20 carbon atoms in the case of benzene and 4 to 18 atoms in the case of naphthalene.

It is further preferred that the hydrocarbyl radical be an alkyl substituent having 10 to 18 carbon atoms and even more preferred that the alkyl substituent contain 12 carbon atoms and be selected from dodecyl and tetrapropyl. Due to commercial availability it is more preferred that the aryl group be a benzene substituted group with an alkyl substituent containing 12 carbon atoms.

The currently most preferred compounds are dodecylbenzenesulfonic acid and tetrapropylbenzenesulfonic acid.

The silanol condensation catalyst may also be a precursor of the Brönstedt acid compound, which includes all of its preferred preferred embodiments, that is, a compound that is converted by hydrolysis into such a compound. Such a precursor is, for example, the anhydrous acid of a sulfonic acid compound, or a sulfonic acid that has been provided with a hydrolysable protecting group such as, for example, an acetyl group, which can be removed by hydrolysis.

In a second preferred embodiment, the Brönstedt acid catalyst is selected from those described in EP 1 309 631 and EP 1 309 632, specifically

a) a compound selected from the group of

(i)

 an alkylated naphthalenemonosulfonic acid substituted with 1 to 4 alkyl groups in which each alkyl group is a linear or branched alkyl with 5 to 40 carbons, each alkyl group being the same or different and in which the total number of carbons in the alkyl groups is in the range of 20 to 80 carbons;

(ii)

 an arylalkyl sulfonic acid in which the aryl is phenyl or naphthyl and is substituted with 1 to 4 alkyl groups in which each alkyl group is a linear or branched alkyl with 5 to 40 carbons, each alkyl group being the same or different and in which the total number of carbons in the alkyl groups is in the range of 12 to 80;

(iii) a derivative of (i) or (ii) selected from the group consisting of an anhydride, an ester, an acetylate, an ester blocked with epoxy and an amine salt thereof which is hydrolyzable in the corresponding alkylnaphthalenemonosulfonic acid or the arylalkyl sulfonic acid;

(iv) a metal salt of (i) or (ii) in which the metal ion is selected from the group consisting of copper, aluminum, tin and zinc; Y

b) a compound selected from the group of

(i) an alkylated aryldisulfonic acid selected from the group consisting of structure (III):

and the structure (IV):

in which each of R1 and R2 is the same or different and is a linear or branched alkyl group with 6 to 16 carbons, and 10 is 0 to 3, z is 0 to 3 with the proviso that y + z is 1 to 4, n is 0 to 3, X is a divalent moiety selected from the group consisting of -C (R3) (R4) - in which each of R3 and R4 is H or independently a linear alkyl group

or branched from 1 to 4 carbons and n is 1; -C (= O) - where n is 1; -S- in which n is 1 to 3 and -S (O) 2- in which n is 1; Y

15 (ii) a derivative of (i) selected from the group consisting of anhydrides, esters, sulphonic acid esters blocked with epoxy, acetylates and amine salts thereof which is hydrolysable in alkylated aryldisulfonic acid,

together with all preferred embodiments of those sulfonic acids described in the aforementioned European patents.

Preferably, in the polyolefin composition, the silanol condensation catalyst is present in an amount of 0.0001 to 6% by weight, more preferably 0.001 to 2% by weight, and most preferably 0.02 to 0, 5% by weight.

The described composition comprises a crosslinkable polyethylene containing hydrolysable silane groups (A). Preferably, the crosslinkable polyolefin preferably consists of a polyethylene containing hydrolysable silane groups.

The hydrolyzable silane groups can be introduced into the polyethylene by copolymerization of, for example, ethylene monomers with comonomers containing silane groups or by grafting, that is, by chemical modification of the polymer by adding silane groups most often in a reaction. by radicals. Both techniques are well known in the art.

Preferably, the polyethylene containing silane groups has been obtained by copolymerization. In the case of polyethylene, the copolymerization is preferably carried out with an unsaturated silane compound represented by the formula

R1SiR2qY3-q (V) 40 in which

R1 is a hydrocarbyl, hydrocarbyloxy or ethylenically unsaturated (meth) acryloxyhydrocarbyl group,

45 R2 is an aliphatic saturated hydrocarbyl group,

And, which may be the same or different, it is a hydrolysable organic group and

q is 0, 1 or 2. 50 Special examples of the unsaturated silane compound are those in which R 1 is vinyl, allyl, isopropenyl,

butenyl, cyclohexanyl or gamma- (meth) acryloxypropyl; Y is methoxy, ethoxy, formyloxy, acetoxy, propionyloxy or an alkyl or arylamino group; and R2, if present, is a methyl, ethyl, propyl, decyl or phenyl group.

A preferred unsaturated silane compound is represented by the formula

CH2 = CHSi (OA) 3 (VI)

wherein A is a hydrocarbyl group having 1-8 carbon atoms, preferably 1-4 carbon atoms.

The most preferred compounds are vinyltrimethoxysilane, vinylbismethoxyethoxysilane, vinyltriethoxysilane, gamma (meth) acryloxypropyltrimethoxysilane, gamma (meth) acryloxypropyltriethoxysilane and vinyltriacetoxysilane.

The copolymerization of ethylene and the unsaturated silane compound can be carried out under any suitable condition producing the copolymerization of the two monomers.

In addition, the copolymerization can be implemented in the presence of one or more comonomers that can be copolymerized with the two monomers. Such comonomers include (a) vinyl carboxylate esters such as vinyl acetate and vinyl pivalate, (b) alpha-olefins such as propene, 1-butene, 1-hexane, 1-octene and 4-methyl-1-pentene, ( c) (meth) acrylates such as (meth) methyl acrylate, (meth) ethyl acrylate and (meth) butyl acrylate,

(d) olefinically unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and fumaric acid, (e) derivatives of (meth) acrylic acid such as (meth) acrylonitrile and (meth) acrylic amide, (f) vinyl ethers such as vinylmethyl ether and vinylphenyl ester, and (g) aromatic vinyl compounds such as styrene and alpha-ethylstyrene.

Among these comonomers, vinyl esters of monocarboxylic acids having 1-4 carbon atoms such as vinyl acetate and (meth) acrylate of alcohols having 1-4 carbon atoms such as methyl (meth) acrylate are preferred.

Especially preferred comonomers are butyl acrylate, ethyl acrylate and methyl acrylate.

Two or more such olefinically unsaturated compounds can be used in combination. The term "(meth) acrylic acid" is intended to encompass both acrylic acid and methacrylic acid. The comonomer content of the copolymer can be 70% by weight of the copolymer, preferably about 0.5 to 35% by weight, most preferably about 1 to 30% by weight.

If a graft polymer is used, it can be produced, for example, by either of the two methods described in US 3,646,155 and US 4,117,195, respectively.

The polyethylene containing silane groups (A) preferably contains from 0.001 to 15% by weight of the silane compound, more preferably from 0.01 to 5% by weight, most preferably from 0.1 to 2% by weight.

The polymer composition may additionally contain various additives such as miscible thermoplastics, antioxidants, other stabilizers, lubricants, fillers, coloring agents and foaming agents.

As an antioxidant, preferably a compound or a mixture of such compounds that is neutral or acidic, must comprise a sterically hindered phenol group or aliphatic sulfur groups. Such compounds are disclosed in EP 1 254 923 which are particularly suitable antioxidants for the stabilization of polyolefins containing hydrolysable silane groups that are crosslinked with a silanol condensation catalyst, in particular an acid silanol condensation catalyst. Other preferred antioxidants are disclosed in WO 2005/003199 A1.

Preferably, the antioxidant is present in the composition in an amount of 0.01 to 3% by weight, more preferably 0.05 to 2% by weight, and most preferably 0.08 to 1.5% by weight.

The silanol condensation catalyst (B) is normally added to the polyethylene containing silane groups (A) by combining the polymer with a so-called mother mixture in which the catalyst, and optionally other additives, are contained in a polymer matrix, for example , polyolefin, in concentrated form.

Therefore, the composition containing titanium dioxide (C) is normally added as a mother mixture, the so-called color mother mixture.

The silanol condensation catalyst (B) and the composition containing titanium dioxide (C) are preferably added to the polyethylene containing silane groups (A) during the manufacturing stage of the finished article, for example, cable extrusion. Commonly, the compositions (B) and (C) are added in a mother mixture form to the composition (A). These stock mixtures are prepared by combination and contain the silanol condensation catalyst and / or the pigment composition in a polymer matrix in concentrated form. Preferably, component (B) and component (C) are added by separate mother mixtures.

The matrix polymer is a polyethylene, which may be a homo- or copolymer of ethylene, for example, low density polyethylene, or copolymer of polyethylene-methyl-ethyl-butyl acrylate containing from 1 to 50% by weight of the acrylate , and mixtures thereof.

As stated, in a mother mixture the compounds to be added to the polyolefin containing silane groups are contained in concentrated form, that is, in an amount much higher than that of the final composition.

The stock mixture preferably comprises component (B) in an amount of 0.3 to 6% by weight, more preferably 0.7 to 3.5% by weight.

Component (C) is preferably present in the stock mixture in an amount of 0.5 to 95% by weight, more preferably 2 to 50% by weight.

The stock mixture is preferably processed with the polymer containing silane group in an amount of 1 to 10% by weight, more preferably 2 to 8% by weight.

The combination can be carried out by any known combination process that includes extruding the final product with a screw extruder press or a kneader.

A process for producing a layer of a wire or cable comprising extrusion of a polyolefin composition according to any one of the above-described embodiments is carried out at a temperature in the range of 140 to 280 ° C.

The following examples serve to further illustrate the present invention.

Examples

1. Measurement procedures

a) Crosslinking performance

The process used to check the compatibility of additives in polyolefin compositions comprising a crosslinkable polyolefin with hydrolyzable silane groups and a Brönstedt acid as a silanol condensation catalyst is described as follows.

The test requires a batch laboratory mixer with a capacity to mix 25 to 500 g and has the option of measuring the melt temperature and the moment of the rotors. It is an advantage if these parameters can be represented during the test. In the present case, a Brabender mixer with rotors having a capacity of 287 cm3 is used. It is estimated that the weights and volumes of the components are 254 cm3. The chamber temperature is set at 120 ° C and the temperature is checked to be stable. The polymer resin is loaded into the chamber in portions. If the resin is molten, additives that are not part of the catalyst master mix are added. These additives may be a color mixture of pigments or fillers or TiO2 (composition containing titanium dioxide) or any other additive that should be tested. After dispersion of the additives in the melt, the catalyst mixture is charged. The melt is further mixed until the initial torque level is stable. Then 20 g of crushed ice, prepared from deionized water and packed in a small polythene plastic bag, are added to the melt and the time, temperature and torque are recorded until curing is completed or during a cure maximum time of 2 h.

The torque increase (momentum) is recorded in the plotter. The speed and degree of crosslinking are calculated from the curve. The degree of cross-linking is determined as the delta between the lowest moment and the peak moment reached, both values being measured at a temperature of 120 ° C, that is, the difference between the highest value of the recorded torque (when the cross-linking is completed) and the lowest torque value (before crosslinking begins, that is, the reference level when ice is added).

b) Melt flow rate

The melt flow rate (MFR) is determined according to ISO 1133 and is indicated in g / 10 min. The MFR is an indication of the flow capacity and, therefore, the processability of the polymer. The higher the melt flow rate, the lower the viscosity of the polymer. The MFR is determined at 190 ° C and can be determined at different loads such as 2.16 kg (MFR2) or 21.6 kg (MFR21).

c) Content of comonomer

The comonomer content (% by weight) was determined in a known manner based on the determination by Fourier transform infrared spectroscopy (FTIR) calibrated with 13C NMR. The peak for the comonomer was compared with the polyethylene peak (for example, the peak for butyl acrylate at 3450 cm-1 was compared with the peak for polyethylene at 2020 cm-1 and the peak for silane at 945 cm-1. compared with the polyethylene peak at 2665 cm -1). 13C NMR calibration is performed in a conventional manner that is well documented in the literature.

5 2. Compositions produced a) Mother mixes

-

a matrix resin: an ethylene-butyl acrylate copolymer with 17% by weight of butyl acrylate, a density of 924 kg / m3 and an MFR2 of 47.0 g / 10 min;

-

a silanol condensation catalyst: linear dodecylbenzenesulfonic acid (DDBSA);

-

a compound containing silicon groups: hexadecyltrimethoxysilane (HDTMS), 15

-

antioxidant: butylated reaction products of 4-methyl-phenol with dicyclopentadiene (Ralox LC, CAS No. 68610-51-5); and 1,3,5-trimethyl-2,4,6-tris- (3,5-di-tert-butyl-4-hydroxyphenyl) benzene (Irganox 1330 ™, CAS No. 1709-70-2).

The components were used in the mother mixtures in the amounts indicated in the following Table 1. The combination of the mother mixtures was performed using a Brabender kneader (small chamber, 47 cm3) and 3 mm thick plates were molded by compression at 180 ° C.

Table 1:

/% by weight Matrix resin 88.5 DDBSA 1.5 HDTMS 4 Antioxidants 6

25 b) Compositions

The stock mixture of Table 1 was processed in an amount of 5% by weight with 94% by weight of a polyethylene containing silane groups having a density of 923 kg / m3, an MFR2 of 0.9 g / 10 min and a content of

30 silane copolymer of 1.3% by weight in a Brabender kneader with 1% by weight of the respective TiO2 powder (see Table 2).

3. Crosslinking performance of different compositions

35 Table 2 shows the different compositions containing titanium dioxide used. The third column facilitates the concentration of titanium dioxide in the composition containing titanium dioxide. The fourth column indicates with "+" or "-" if the titanium dioxide in the compound containing titanium dioxide used is coated or not, respectively. Similarly, the fifth column contains information about the presence of a silicon-containing coating. Finally, the sixth column indicates the crosslinking performance providing the difference in

40 the torque measured at the highest point after the end of the cross-linking and the lowest point before the start of the cross-linking, at 120 ° C.

Table 2:

TiO2 /% in Coating Coating �weight containing (pair of

torsion silicon) / Nm Example 1 Kemira AN 98 --55 Example 2 Tioxide AHR 98 --55 Example 3 Tioxide RFC5 97 + + 47 Example 4 Tioxide TR28 97 + -44 Example 5 Kemira 300 97 + -41 Example 6 Kemira RD3 93 + -41 Example 7 Kemira 405 96 + + 34 Example 8 Kemira 660 93 + + 32 Example 9 Kemira RDE2 88 + + 27

Example 10 Tioxide RTC30 92 + + 26 Example 11 Thioxide APP2 96 + + 21

The larger � (torque), the better the crosslinking. The presence of a coating and the type of coating is decisive for performance. A silicon-containing coating is more sensitive than a silicon-free coating.

Claims (5)

1. Use of a polyolefin composition for the production of a layer of a wire or cable, in which the polyolefin composition comprises

(i)

 a crosslinkable polyethylene with hydrolysable silane groups (A),

(ii)

 a silanol condensation catalyst (B) which is a Brönstedt acid (B), and

(iii) a composition containing titanium dioxide (C), a) which does not comprise a silicon-containing coating and the concentration of titanium dioxide in said composition containing titanium dioxide is at least 93% by weight, or b) the titanium dioxide in said composition containing titanium dioxide is coated, coating containing silicon, and the concentration of titanium dioxide in said composition containing titanium dioxide is at least 97% by weight. characterized in that the difference between the highest torque value, measured when crosslinking is completed or after a maximum reaction time of 2 h, and the lowest torque value, before crosslinking begins, is 40 Nm or higher, according to which both values are measured at 120 ° C using a batch laboratory mixer with a capacity to mix 25 to 500 g and that has the option of measuring the temperature of the melt and the moment of the rotors.

2.

Use of a polyolefin composition according to claim 1, wherein the difference in the torque measured at 120 ° C is 44 Nm or greater.

3.

Use of a polyolefin composition according to claim 1, wherein the difference in the torque measured at 120 ° C is 45 Nm or greater.

Four.

Use of a polyolefin composition according to claim 1, wherein the concentration of titanium dioxide in said composition containing titanium dioxide is at least 97% by weight.

5.

Use of a polyolefin composition according to any one of claims 1 to 4, wherein the titanium dioxide in said composition containing titanium dioxide (C) is not coated.